Surface energy balance closure in an arid region: role of soil heat flux

The large soil heat fluxes in hot desert regions are very important in energy balance studies. Surface energy balance (SEB) observations, however, reveal that there is an imbalance in surface flux measurements and that it is difficult to isolate those flux measurements causing the imbalance errors. In this paper a new approach was tested focusing on a high temporal resolution of soil heat flux measurements at the surface. To determine if improved soil heat flux measurements could be obtained for a sandy desert, a standard soil heat flux sensor was buried at the surface of a playa and covered with less than 1 mm of playa soil, as opposed to burial several centimetres deep. It was anticipated that this would permit direct surface soil heat flux measurements. A field campaign was carried out in September and October in 1997 and for the same period in 2000, in a sandy desert belt situated in Nizzana, NW Negev, Israel. The research was designed to examine the separate components of the SEB. The location was considered ideal since only the soil heat flux and sensible heat flux are balanced by the net radiation. This new approach was compared to traditional soil heat flux measurements. The resulting energy balance closure was found to be very good. The results suggest that this method could be used as a reference surface soil heat flux measurement. Further examination of the energy balance closure is needed over a range of land surface types.